Why is one plant lagging behind the others in growth?

Hey, you need to water on a daily basis. Way more frequently when growing in cocosoil. It is true that your plant needs more nutrients, But your All-In-One should still work and theres not much you can change, but adding Cal-Mag. Happy Growing and dont stress it, if you water more often and smaller amounts she will grow normal. She also could be behind just because of the genetics dont worry about it too much, as long as she looks rather healthy.